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  • The Company of Biologists  (11)
  • 1990-1994  (11)
  • 1
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    Online Resource
    Locomotor Performance and Energetic Cost of Sidewinding by the Snake Crotalus Cerastes
    The Company of Biologists ; 1992
    In:  Journal of Experimental Biology Vol. 163, No. 1 ( 1992-02-01), p. 1-14
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 163, No. 1 ( 1992-02-01), p. 1-14
    Abstract: We measured the performance (burst speed and endurance) and the energetic cost of sidewinding locomotion for the viperid snake Crotalus cerastes. The linear scaling regressions relating log mass to log burst speed and log endurance have slopes of 0.29 and 1.01, respectively. Maximal burst speed observed for an individual snake (SVL=41.9cm, SVL is snout-vent length) was 3.7 km h1. Adult snakes were able to match a tread speed of 0.5 km h−1 for times ranging from 33 to more than 180 min, and at 0.7 km h−1 endurance times ranged from 9 to 52 min. Rates of oxygen consumption increased linearly over a range of aerobically sustainable speeds (0.28−0.50 km h−1), with a resulting net cost of transport (NCT) of 0.408 ml O2g−1 km−1 for eight snakes with a mean mass of 110g. Sidewinding of C. cerastes involves periodic movements with a frequency that increases linearly with mean forward speed. At 0.50 km h-1, the mean (N=8) mass-specific energetic cost per cycle of movement was 0.28μl O2g−1cycle−1 for sidewinding. The NCT and the cost per cycle of movement of C. cerastes sidewinding are significantly less than those of similar mass snakes (Coluber constrictor) performing either terrestrial lateral undulation or concertina locomotion. The NCT of C. cerastes sidewinding is also significantly less than that predicted for the terrestrial limbed locomotion of lizards of similar mass. Mean C. cerastes (0.405 ml O2g−1h−1) is only about half that reported for C. constrictor; however, the mean endurance at 0.60 km h−1 (73 min) for sidewinding C. cerastes does not differ significantly from that reported for C. constrictor laterally undulating.
    Type of Medium: Online Resource
    ISSN: 0022-0949 , 1477-9145
    URL: Article
    DOI: 10.1242/jeb.163.1.1
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1992
    detail.hit.zdb_id: 1413561-9
    detail.hit.zdb_id: 1482461-9
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  • 2
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    Is Walking Costly For Anurans? the Energetic Cost of Walking in the Northern Toad Bufo Boreas Halophilus
    The Company of Biologists ; 1994
    In:  Journal of Experimental Biology Vol. 197, No. 1 ( 1994-12-01), p. 165-178
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 197, No. 1 ( 1994-12-01), p. 165-178
    Abstract: Locomotor mode and the maximal capacity for aerobic metabolism are thought to be co-adapted in anuran amphibians. Species that rely heavily on walking often have high capacities for aerobic metabolism relative to species that rely primarily on saltation. We tested the hypothesis of co-adaptation of gait and aerobic metabolism by investigating the locomotor energetics of Bufo boreas halophilus, a toad that walks, but does not hop. Rates of oxygen consumption during locomotion were measured in an enclosed variable-speed treadmill. The steady-state rate of oxygen consumption increased linearly within a range of sustainable speeds [ (ml O2 g−1 h−1) = 0.93 X speed (km h−1) + 0.28]. The minimum cost of transport, Cmin (the slope of this relationship), varied significantly among individual toads. When expressed in units of oxygen consumed per distance travelled (ml O2 km−1), Cmin scaled isometrically with body mass: Cmin = 0.69mass1.07. Consequently, mass-specific Cmin (ml O2 g−1 km−1) was uncorrelated with body mass. Variation in Cmin was also unrelated to experimental temperature. Mass-specific Cmin estimates were similar to previous allometric predictions for terrestrial animals of similar size, which contrasts with previous findings for another toad species. Maximum rates of oxygen consumption measured in closed, rotating respirometers were significantly higher than the maximum rates achieved on the treadmill, but lower than those measured previously in other Bufo species. Our results indicate that walking is not necessarily a costly gait for toads and that high maximum rates of oxygen consumption are not associated with reliance on walking within the genus Bufo.
    Type of Medium: Online Resource
    ISSN: 0022-0949 , 1477-9145
    URL: Article
    DOI: 10.1242/jeb.197.1.165
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1994
    detail.hit.zdb_id: 1413561-9
    detail.hit.zdb_id: 1482461-9
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  • 3
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    Muscle Recruitment During Terrestrial Locomotion: How Speed and Temperature Affect Fibre Type Use in a Lizard
    The Company of Biologists ; 1990
    In:  Journal of Experimental Biology Vol. 152, No. 1 ( 1990-09-01), p. 101-128
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 152, No. 1 ( 1990-09-01), p. 101-128
    Abstract: Synchronized electromyography and cinematography were used to study the activity of the red and white regions of the iliofibularis muscle in savannah monitor lizards, Varanus exanthematicus (Bosc), during locomotion. Analysis of variance on results from four individuals moving at speeds of up to 1.5 km h−1 at two body temperatures (25 and 35 °C) revealed that all kinematic variables were significantly affected by speed but none was affected by temperature. Hence, patterns of limb movement at any speed were similar at both temperatures. However, this similarity resulted from differences in muscle activity. Analysis of variance on electromyographic variables for activity in the red and white regions showed widespread significant effects of both temperature and speed. The red region was active at all speeds, and it displayed regular bursts of activity which usually occurred when the foot was above the ground, the femur was being abducted and the knee flexed. Variables measuring the intensity of red region activity generally increased with speed until a maximum was attained and no further change occurred with additional increases in speed. The speed at which maximum red activity was attained at 25 °C was less than that at 35 °C. For equal locomotor speeds, amplitudes of electromyograms (EMGs) from the red region at 25 °C were greater than those at 35°C. In contrast to the red region, the white region was active only above some threshold speed, and activity was often rather irregular compared to that of the red region. At 25°C the threshold speed for recruitment of the white region (0.9kmh−1) was less than that at 35°C (1.3kmh−1). The relationship between locomotor speed and activity per minute for the red region was very similar to the relationship between speed and rate of oxygen consumption described in previous studies of lizards, and the threshold speed for recruitment of the white region was also similar to the maximal aerobic speed previously reported for this species. Hence, lizards increase speed and compensate for lower temperature by increasing intensity of activity within the red region and recruiting fibres in the white region. We suggest that compensation for muscle function at decreased body temperature may involve recruitment of greater numbers of motor units.
    Type of Medium: Online Resource
    ISSN: 0022-0949 , 1477-9145
    URL: Article
    DOI: 10.1242/jeb.152.1.101
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1990
    detail.hit.zdb_id: 1413561-9
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  • 4
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    Temperature, Muscle Power Output and Limitations on Burst Locomotor Performance of the Lizard Dipsosaurus Dorsalis
    The Company of Biologists ; 1993
    In:  Journal of Experimental Biology Vol. 174, No. 1 ( 1993-01-01), p. 185-197
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 174, No. 1 ( 1993-01-01), p. 185-197
    Abstract: The mechanical power output of fast-twitch fibres from the iliofibularis of the lizard Dipsosaurus dorsalis was measured over a broad body temperature range using the oscillatory work-loop technique. The optimal cycling frequency, that frequency at which mechanical power output is maximal, increases with temperature from 3.3Hz at 15°C to 20.1Hz at 42°C. Maximum power output increases with temperature, from 20 W kg-1 at 15°C to 154 W kg-1 at 42°C, the largest power output yet measured using the work-loop technique. At low temperatures (15°C and 22°C), stride frequency during burst running is nearly identical to the optimal cycling frequency for in vitro power output, suggesting that maximum power output may limit hindlimb cycle frequency in vivo. However, at higher temperatures (35°C and 42°C), the optimal cycling frequency of the isolated muscle is significantly higher than the burst stride frequency, demonstrating that contractile events no longer limit hindlimb cycle frequency. At higher temperatures, it is thus unlikely that the fast-twitch fibres of this muscle in vivo attain their potential for maximum power output.
    Type of Medium: Online Resource
    ISSN: 0022-0949 , 1477-9145
    URL: Article
    DOI: 10.1242/jeb.174.1.185
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1993
    detail.hit.zdb_id: 1413561-9
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  • 5
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    The Evolution of Activity Capacity
    The Company of Biologists ; 1991
    In:  Journal of Experimental Biology Vol. 160, No. 1 ( 1991-10-01), p. 1-23
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 160, No. 1 ( 1991-10-01), p. 1-23
    Abstract: The capacities of animals for activity (burst speed, maximal exertion, endurance) are examined in relation to their selective importance in extant populations and the pattern of their evolution in major animal taxa. Activity capacities have been demonstrated to be both heritable and highly variable in natural populations and hence susceptible to natural selection. Some field studies have demonstrated significant positive associations between activity capacities, particularly burst speed, and survivorship; other studies have not. The potential for such selection therefore clearly exists, although it may not operate in all populations. Comparative studies of major taxa have linked endurance capacities to maximal rates of oxygen consumption; speed and exertion are correlated with capacities for anaerobic metabolism, either the catabolism of phosphagens or the production of lactic acid or octopine, depending on taxon. In vertebrates, the primitive metabolic pattern involved the use of aerobic metabolism to support moderate swimming performance, supplemented by bursts of activity fuelled through lactic acid production. Because of much greater locomotor costs, the transition of vertebrates onto land entailed a decrease in endurance, which was greatly expanded again only after the evolution of the higher rates of aerobic metabolism characteristic of the birds and mammals. These greater aerobic capacities may have been selected for thermoregulatory reasons and/or for increased activity capacity itself.
    Type of Medium: Online Resource
    ISSN: 0022-0949 , 1477-9145
    URL: Article
    DOI: 10.1242/jeb.160.1.1
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1991
    detail.hit.zdb_id: 1413561-9
    detail.hit.zdb_id: 1482461-9
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  • 6
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    Mox-1 and Mox-2 define a novel homeobox gene subfamily and are differentially expressed during early mesodermal patterning in mouse embryos
    The Company of Biologists ; 1992
    In:  Development Vol. 116, No. 4 ( 1992-12-01), p. 1123-1136
    Details
    In: Development, The Company of Biologists, Vol. 116, No. 4 ( 1992-12-01), p. 1123-1136
    Abstract: We have isolated two mouse genes, Mox-1 and Mox-2 that, by sequence, genomic structure and expression pattern, define a novel homeobox gene family probably involved in mesodermal regionalization and somitic differentiation. Mox-1 is genetically linked to the keratin and Hox-2 genes of chromosome 11, while Mox-2 maps to chromosome 12. At primitive streak stages (approximately 7.0 days post coitum), Mox-1 is expressed in mesoderm lying posterior of the future primordial head and heart. It is not expressed in neural tissue, ectoderm, or endoderm. Mox-1 expression may therefore define an extensive ‘posterior’ domain of embryonic mesoderm before, or at the earliest stages of, patterning of the mesoderm and neuroectoderm by the Hox cluster genes. Between 7.5 and 9.5 days post coitum, Mox-1 is expressed in presomitic mesoderm, epithelial and differentiating somites (dermatome, myotome and sclerotome) and in lateral plate mesoderm. In the body of mid-gestation embryos, Mox-1 signal is restricted to loose undifferentiated mesenchyme. Mox-1 signal is also prominent over the mesenchyme of the heart cushions and truncus arteriosus, which arises from epithelialmesenchymal transformation and over a limited number of craniofacial foci of neural crest-derived mesenchyme that are associated with muscle attachment sites. The expression profile of Mox-2 is similar to, but different from, that of Mox-1. For example, Mox-2 is apparently not expressed before somites form, is then expressed over the entire epithelial somite, but during somitic differentiation, Mox-2 signal rapidly becomes restricted to sclerotomal derivatives. The expression patterns of these genes suggest regulatory roles for Mox-1 and Mox-2 in the initial anteriorposterior regionalization of vertebrate embryonic mesoderm and, in addition, in somite specification and differentiation.
    Type of Medium: Online Resource
    ISSN: 0950-1991 , 1477-9129
    URL: Article
    DOI: 10.1242/dev.116.4.1123
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1992
    detail.hit.zdb_id: 1411623-6
    detail.hit.zdb_id: 2007916-3
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  • 7
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    Body Size, Muscle Power Output and Limitations on Burst Locomotor Performance in the Lizard Dipsosaurus Dorsalis
    The Company of Biologists ; 1993
    In:  Journal of Experimental Biology Vol. 174, No. 1 ( 1993-01-01), p. 199-213
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 174, No. 1 ( 1993-01-01), p. 199-213
    Abstract: The power output of fast-glycolytic (FG) muscle fibres isolated from the iliofibularis (IF) muscle of desert iguanas (Dipsosaurus dorsalis) was measured at 35°C using the oscillatory work-loop technique. To simulate cyclical muscle length changes during running, isolated fibre bundles were subjected to sinusoidal length changes and phasic stimulation during the strain cycle. At constant strain (12%), the duration and timing (phase) of stimulation were adjusted to maximise power output. Using both hatchlings (4–8g) and adults of varying sizes (15–70g), the intraspecific allometries of IF length and contractile properties were described by regression analysis. The muscle length at which isometric force was maximum ( L0, mm) increased geometrically with body mass (M, g) (L0=5.7M0.33). Maximum power output and the force produced during shortening showed no significant relationship to body size; work output per cycle (Wopt, Jkg−1) under conditions required to maximise power did increase with body size (Wopt=3.7M0.24). Twitch duration (Td, ms), measured from the onset of force generation to 50% relaxation, increased allometrically with body mass (Td=12.4M0.18). Limb cycling frequency during burst running (f, reported in the literature) and the frequency required to maximise power output in vitro (fopt) decreased with body size, both being proportional to body mass raised to the power 0.24. These findings suggest that limb cycling frequency may be limited by twitch contraction kinetics. However, despite corresponding proportionality to body size, limb cycling frequencies during burst running are about 20% lower than the cycling frequencies required to maximise power output. Differences in the contractile performance of the IF in vitro and in vivo are discussed in relation to constraints imposed by gravitational forces and the design of muscular, nervous and skeletal systems.
    Type of Medium: Online Resource
    ISSN: 0022-0949 , 1477-9145
    URL: Article
    DOI: 10.1242/jeb.174.1.199
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1993
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  • 8
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    The Mechanism Of Tongue Projection In Chameleons: I. Electromyographic Tests Of Functional Hypotheses
    The Company of Biologists ; 1992
    In:  Journal of Experimental Biology Vol. 168, No. 1 ( 1992-07-01), p. 1-21
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 168, No. 1 ( 1992-07-01), p. 1-21
    Abstract: In this paper we document the activity of key muscles of the tongue, hyobranchia! apparatus and head during prey capture in the lizard Chamaeleo jacksonii Boulenger and use these data to test current hypotheses of chameleon tongue function. Electromyographic recordings were made during 27 feedings from nine individuals and synchronized with high-speed video recordings (200fields s−1), permitting an assessment of the activity of muscles relative to the onset of tongue projection, contact between tongue and prey, and tongue retraction. Four major results were obtained. (1) The hyoglossi muscles exhibit a single burst of activity that begins between 10 ms before and 20 ms after the onset of tongue projection and continues throughout the period of tongue retraction. (2) The accelerator muscle exhibits a biphasic activity pattern, with the first burst lasting about 185 ms and ending an average of 10.6 ms prior to the onset of projection. (3) The accelerator muscle shows regional variation in morphology that corresponds with variation in motor pattern. The anterior region of the muscle, unlike the posterior portion, exhibits only a single burst of activity that begins 2.5 ms after the onset of tongue projection and is thus not involved in launching the tongue. (4) The geniohyoidei, sternohyoidei, sternothyroidei, depressor mandibulae, adductor mandibulae and pterygoideus all exhibit activity patterns consistent with previously reported kinematic patterns and their proposed roles. The major implications of these results for models of the chameleon feeding mechanism are (1) that the hyoglossi do not act to hold the tongue on the entoglossal process during a loading period prior to tongue projection, and (2) that the presence of 185 ms of intense activity in the accelerator muscle prior to tongue projection suggests the presence of a preloading mechanism, the nature of which is the subject of the companion paper.
    Type of Medium: Online Resource
    ISSN: 0022-0949 , 1477-9145
    URL: Article
    DOI: 10.1242/jeb.168.1.1
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1992
    detail.hit.zdb_id: 1413561-9
    detail.hit.zdb_id: 1482461-9
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  • 9
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    The Mechanism of Tongue Projection in Chameleons: II. Role of Shape Change in a Muscular Hydrostat
    The Company of Biologists ; 1992
    In:  Journal of Experimental Biology Vol. 168, No. 1 ( 1992-07-01), p. 23-40
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 168, No. 1 ( 1992-07-01), p. 23-40
    Abstract: In this paper we investigate the interaction between the accelerator muscle (the muscle that powers tongue projection) and the entoglossal process (the tongue’s skeletal support) that occurs during tongue projection in chamaeleonid lizards. Previous work has shown that there is a delay of about 185 ms between the onset of accelerator muscle activity and the onset of tongue projection. In conjunction with anatomical observations, in vitro preparations of the accelerator muscle mounted on isolated entoglossal and surrogate processes were stimulated tetanically, and the resulting movements were recorded on video at 200 fields s−1. Three results indicate that morphological features of the entoglossus and the accelerator muscle delay the onset of tongue projection following the onset of accelerator contrac-tion: ( 1) the entoglossus is parallel-sided along the posterior 90% of its shaft, only tapering at the very tip, (2) the sphincter-like portion of the accelerator muscle, which effects tongue projection, makes up the posterior 63% of the muscle and does not contact the tapered region of the entoglossus at rest, and (3) accelerator muscles mounted on the entoglossus undergo longitudinal extension and lateral constriction for 83 ms following the onset of electrical stimulation, before projecting off the entoglossus. It is proposed that, during elongation of the accelerator muscle, the sphincter-like region ultimately comes into contact with the tapered region of the entoglossus, causing the onset of projection. This conclusion is supported by the observation that the time between the onset of stimulation and the onset of projection was longer in preparations with surrogate entoglossal processes that had no tapered tip and shorter with surrogate processes that had a tapered tip about four times as long as the natural entoglossus. Tetanically stimulated accelerator muscles reached 90% of peak force 110 ms after the onset of stimulation, indicating that the 185 ms delay between the onset of accelerator activity and the onset of projection seen in vivo allows the accelerator to achieve peak force prior to the onset of projection. Thus, the delay in projection may be crucial in maximizing the acceleration and velocity achieved by the projected chameleon tongue.
    Type of Medium: Online Resource
    ISSN: 0022-0949 , 1477-9145
    URL: Article
    DOI: 10.1242/jeb.168.1.23
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1992
    detail.hit.zdb_id: 1413561-9
    detail.hit.zdb_id: 1482461-9
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  • 10
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    Kinematics of Tongue Projection in Chamaeleo Oustaleti
    The Company of Biologists ; 1991
    In:  Journal of Experimental Biology Vol. 159, No. 1 ( 1991-09-01), p. 109-133
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 159, No. 1 ( 1991-09-01), p. 109-133
    Abstract: The kinematics of prey capture by the chamaeleonid lizard Chamaeleo oustaleti were studied using high-speed cinematography. Three feeding sequences from each of two individuals were analyzed for strike distances of 20 and 35 cm, at 30°C. Ten distances and angles were measured from sequential frames beginning approximately 0.5 s prior to tongue projection and continuing for about 1.0 s. Sixteen additional variables, documenting maximum excursions and the timing of events, were calculated from the kinematic profiles. Quantified descriptions of head, hyoid and tongue movements are presented. Previously unrecognized rapid protraction of the hyobranchial skeleton simultaneously with the onset of tongue projection was documented and it is proposed that this assists the accelerator muscle in powering tongue projection. Acceleration of the tongue occurred in about 20ms, reaching a maximum acceleration of 486 m s−2 and maximum velocity of 5.8m s−1 in 35 cm strikes. Deceleration of the tongue usually began within 5 ms before prey contract and the direction of tongue movement was reversed within 10 ms of prey contact. Retraction of the tongue, caused by shortening of the retractor muscles, reached a maximum velocity of 2.99 ms−1 and was complete 330 ms after prey contact. Projection distance influences many aspects of prey capture kinematics, particularly projection time, tongue retraction time and the extent of gape and head movements during tongue retraction, all of which are smaller in shorter feedings. Though several features of the chameleon strike have apparently been retained from lizards not capable of ballistic tongue projection, key differences are documented. Unlike members of a related family, the Agamidae, C. oustaleti uses no body lunge during prey capture, exhibits gape reduction during tongue projection and strongly depresses the head and jaws during tongue retraction. Note: Present address: Department of Biological Sciences, Florida State University, Tallahassee, FL 32306, USA.
    Type of Medium: Online Resource
    ISSN: 1477-9145 , 0022-0949
    URL: Article
    DOI: 10.1242/jeb.159.1.109
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1991
    detail.hit.zdb_id: 1413561-9
    detail.hit.zdb_id: 1482461-9
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